Salix is a linux distribution based on Slackware that is simple and easy to use. Salix aims to be completely backwards compatible with Slackware, so Slackware users can benefit from Salix repositories.

OpenThinClient is an Open Source Thin Client Solution consisting of a Linux based operating system along with a comprehensive Java based management GUI and server component. It's designed to manage and support a great number of Thin Clients efficiently.

andLinux is a complete Ubuntu Linux system running seamlessly in Windows 2000 based systems (2000, XP, 2003, Vista, 7; 32-bit versions only). It is not just for development and runs almost all Linux applications without modification.

Note: These are not official TKL appliances but appliances built and supplied by leading community members.
TurnKey Linux is an opensource project that aims to develop high-quality software appliances that are easy to deploy, easy to use and free. http://www.turnkeylinux.org/

FreeOS/1 is a Free, Open Source, FreeDOS based Free and Open Source Alternative OS, with open source Microsoft Windows compatibility using HXDOSExtender KernelEx,and ReactOS source code. FreeOS/1 will include new technologies and will be easy to use

The Ekaaty project is an free, robust, secure and friendly operative system developed with community participation. It's focused to provides brazilian user's specifics necessities and designed for optimized use of disc space and machine resources.

ELKS is a subset of the Linux kernel that runs on IBM compatible PCs from 8086 up. It is intended to get use out of obsolete old hardware, for use in embedded systems, and as an educational tool.
ELKS has been moved to Github to protest SourceForge's installer adware hijacking. This does not directly affect ELKS, but it does affect many major open source projects such as Gimp and FileZilla by attempting to trick the user into installing adware in order to download these programs. I refuse to leave ELKS here with such policies in effect. If you have questions about this, please email jody@c02ware.com.

A set of tools to build your own customed Linux distribution with more managability than raw LFS(Linux From Scratch). Include source package manager, file system backup and realtime mirror apps, and some assistant data structure writen in Python, etc...

pup2p is a remaster of the Puppy Linux livecd distro and is aimed at use with the anonymous network I2P. It includes I2P as well as a number of I2P related apps.
NOTE: The ISO is currently VERY out of date! Sorry for my absence. I may try to update the project soon. The SFS file IS up to date as of this change. 03/2013

uDOS is a free operating system built on the FreeDOS kernel with DJGPP. uDOS provides an integrated suite of features inluding Perl, Python, etc., as well as a Watt-32 based networking environment and ELF library support. Can be run live from CD image.